Installing Kohler sliding glass shower door:

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I need to drill 6 holes, 3 in each side jamb, into new, very hard porcelain tile.

Diamond bits are expensive, just a DIY'er here!

Considering drilling 3 new holes in each jamb, to line up with the grout lines. Then fill the old holes with steel/zinc plated hole plugs (tried one of the plugs, looks fine, also not exactly in a noticeable place.)

Any thoughts on this? TIA

The plugs will probably rust - if you do this, I'd consider a plastic plug.

Lowes sells Hitachi diamond core bits that, at least in the smaller sizes, aren't too bad and should last at least long eough to drill your six holes - less than $20. If you buy one on-line, you can get lesser quality ones (and better, if you want to pay for it!) cheaper, even with shipping. Make sure the hole is big enough so the screw fits through easily. If you have wood backing behind, you can use a longer screw and go into the wood. If you want to use the plastic inserts, you'll need a larger hole, and the bits get more expensive. Keep in mind, the screw really isn't holding much in tension, only shear, so it really doesn't have to have super support.

The key to using any core bit is start the hole by tipping the drill at a low angle to use the edge to make a divot while running the drill slowly, than slowly rotate the drill until you've got it perpendicular to the wall. Use a spray bottle with water to keep things wet and don't press hard...let the diamonds grind the hole.

We just fill the old holes with silicone caulking and smooth it even with the tile surface. Better looking than any metal repair.

OK, guys, thanks. I guess I'll try to drill at least one hole; if it doesn't seem doable I'll switch to plan B.

Jadnashua: Can you explain....

I'm not sure what you mean when you say that "the screw really isn't holding much in tension, only shear". TIA.

You are not trying to pull the door off the wall, "tension",and the framework would prevent it even if you tried. The anchor only has to keep it from sliding sideways, which is "shear". Even a "smooth pin" would work if you could get it to look good.

Got it, HJ, thanks.

Managed to drill the 6 holes. About 10 minutes each, very slow, plenty of water spray, two Hitachi diamond bits. Wouldn't want to do that very often, but it's done!